With the rapid development of Internet, the scale of Internet becomes larger and larger, applications over Internet becomes more and more complicated, and the requirement for the controllability of Internet becomes higher and higher. In view of this, clean slate research group of Stanford University proposes the network architecture of software defined network (SDN), of which the core technology named OpenFlow realizes flexible control of the network traffic through separating the control plane from the data plane of the network apparatus. OpenFlow is an exchange technology, in which the OpenFlow protocol is configured to establish the software defined network, and the network could be managed and controlled as a whole instead of as lots of standalone apparatus.
The bearer and the control are separated from each other in IP layer or above IP layer in conventional SDN, that is, this mainly involves an improvement on the core network level, and wireless SDN is directed to a solution for separating the control from the bearer in the wireless access network.
The network architecture of wireless SDN is shown in FIG. 1. The wireless SDN separates the control plane from the user plane in the wireless network entity, and realizes the wireless access bearer control based on OpenRadio protocol and the control of the network layer and data transfer based on OpenCore protocol. The wireless SDN includes the control plane and the user plane entities. The control plane includes a Single Network Controller (SNC) and a control-plane of node B (cNB). The user plane includes a Gateway Router (GR) and a user-plane of node B (uNB). SNC is a centralized network control point and controls the data flow routing through OpenCore protocol. cNB realizes wireless resource management of the wireless parameter control on uNB through OpenRadio protocol.
A group session service refers to the multi-people session in the network at present, such as push to talk over cellular (PoC), instant message (IM), and video conference. Taking a PoC service as an example, the PoC service is a push-to-talk service defined by Open Mobile Architecture (OMA) and The 3rd Generation Partnership Project (3GPP) based on the public cellular mobile communication network, and realizes communications similar to a group session through the half duplex VoIP technology. The user only needs to press a key like using an interphone and needs not to dial to enable point-to-multipoint instant communications with multiple users from anywhere quickly and directly.
The functions of respective network elements in a PoC are as follows.
A PoC Client is responsible for login to a PoC service, initiating, participating and terminating a PoC session, coding, decoding, sending and receiving of PoC voice packets, and so on.
A PoC Server is responsible for network functions on the application layer in the PoC service, which are grouped into a controlling PoC function (CPF) and a participating PoC function (PPF). CPF is responsible for centralized processing of PoC sessions, centralized distribution of media, session right arbitration, spokesman identification, processing of SIP sessions, management of information about participants and media, support for centralized billing, translation of media encoding format, etc. PPF is responsible for processing of the PoC sessions, user plane adaptation, relaying the control information of Talk Burst between a PoC client and a Controlling PoC server, processing of the SIP sessions, providing protocol implementation charging reports of session parties and protocol negotiation for session burst sequences for a joined PoC session, and storing existing answer modes and selecting disabled parameters of a join-to PoC session for a PoC client.
Both of the signaling and data in the conventional group session service need to be forwarded by an application server, thus the load of the server is heavy, and implementation cost is high. Also, a high delay of service data is caused, especially in case of one-to-multi session. A private network is used to achieve a low delay for the PoC session service, which results in a large deployment cost for the service provider.